Problem: Stephanie is 5 times as old as Vanessa and is also 20 years older than Vanessa. How old is Stephanie?
Explanation: We can use the given information to write down two equations that describe the ages of Stephanie and Vanessa. Let Stephanie's current age be $s$ and Vanessa's current age be $v$ $s = 5v$ $s = v + 20$ Now we have two independent equations, and we can solve for our two unknowns. One way to solve for $s$ is to solve the second equation for $v$ and substitute that value into the first equation. Solving our second equation for $v$ , we get: $v = s - 20$ . Substituting this into our first equation, we get the equation: $s = 5$ $(s - 20)$ which combines the information about $s$ from both of our original equations. Simplifying the right side of this equation, we get: $s = 5s - 100$ Solving for $s$ , we get: $4 s = 100$ $s = 25$.